A traditional radio access network (RANs) consist of many individual stand-alone base stations, each having an antenna, equipment for transmitting and receiving radio signals (radio frequency part) and data processing equipment. The base stations are connected to a local exchange in the case of GSM and UMTS mobile systems, or directly to the service gateway and Mobility Management Entity for user and control planes respectively, of the core network in the case of a LTE network. This means that each base station needs an individual backhaul transportation, as well as further systems such as cooling, back up battery, monitoring system.
A recent approach is centralization of radio base stations, in which a radio frequency part and processing equipment of the radio base station are split in two parts and placed in different sites. Processing equipment, termed a digital unit (DUs) is located in a common site, e.g. termed a baseband hotel. The DU offers processing resources for multiple radio cells. The radio frequency part is formed by the radio termination and by the antennas, and may be termed Remote Radio Units (RRUs).
Even though the typical average traffic load in a base station is comparatively low, the functions of the based station are often dimensioned for peak traffic. The utilization rate is low because the average network load is often far lower than that in peak load, due to fluctuations and burstiness of mobile traffic with time. Therefore, the network is overprovisioned in order to handle peak load at each base station.
In some examples, mobile traffic in a business area during the working hours can be greater than evening time; while in residential areas traffic peaks may occur during the evening. During working hours, a part of mobile backhaul which serves the business area is heavily loaded, while a part which serves the residential area is under loaded. During evening time, traffic peaks move to residential area, so the part of the mobile backhaul which serves this area is heavily loaded or overloaded, and the part related to business is under loaded. The resulting need for overprovisioning of entire network resources results in an inefficient use of resources.